• 08-11-2004, 12:14 PM
    kexodusc
    Is there a "scientific method" to setting a subwoofer's phase alignment?
    The last few days I've been playing with the variable phase on my subwoofer, trying to find the "right spot". Is there a proven "method" to doing this properly, or is just a trial-and-error, whatever sounds best kind of thing?
  • 08-11-2004, 12:55 PM
    dmb_fan
    I set the variable phase on my subwoofer by playing an 80Hz tone (the crossover frequency between sub and main speakers) simultaneously through sub and main speakers, and measuring the SPL of the tone at the listening position while adjusting the phase. When the tone is loudest, the subwoofer is in phase with the main speakers.

    I don't know if this is fool proof in every application or not. But I've taken a lot of measurements with 1/6 octave tones and sine wave sweeps, and the frequency response in my room is excellent above, below and throughout the crossover region.

    Hope this helps,
    Adam
  • 08-11-2004, 02:32 PM
    Jimmy C
    I honestly can't hear too much of...
    ..a difference between settings. Maybe a larger room would reveal such things.

    The only thing I can tell you is have a friend flip the switch while you are in the "sweet spot". Whatever sounds best, question yourself about REALLY hearing a difference and buy a new piece of equipment :^)

    Err... I was serious about that listening experiment...
  • 08-11-2004, 02:48 PM
    kexodusc
    Yeah, the lady's been helping me so far...I don't hear a huge difference, but I definitely hear a difference...I have my cutoff quite low though, 60Hz and even 40Hz at times, maybe this makes the impact less prominent?
    I was just curious...I hadn't ever tried the phase knob on either of these since I've owned them...I was always happy enough...I'm not going to lose sleep over this...just curious. You always want to know if you could be missing something.
  • 08-11-2004, 03:05 PM
    dmb_fan
    One might not notice much of a difference if the phase control is a two way switch. It's unlikely that one position will be completely in phase and the other position will be completely out of phase. After all, if one position is 90 degrees out of phase one way and the other position is 90 degrees out of phase the other way, you won't hear a difference at all.

    But playing a tone at the crossover frequency and adjusting the knob on an infinitely variable phase control, you should be able to hear a vast difference between in-phase and out of phase. As you move the control around, you'll find the quietest spot where the speaker and subwoofer are 180 degrees out of phase and they are cancelling each other out almost completely, and you'll find the loudest spot where sub and speaker are in-phase. Keep the knob at the loudest spot.

    You can download sine waves at any frequency at a number of sites. You can also buy a test CD at stryke.com or stereophile.com

    -Adam
  • 08-11-2004, 07:59 PM
    TinHere
    Quote:

    Originally Posted by kexodusc
    The last few days I've been playing with the variable phase on my subwoofer, trying to find the "right spot". Is there a proven "method" to doing this properly, or is just a trial-and-error, whatever sounds best kind of thing?

    Here's a blurb from an e-mail about R-DES:

    "R-DES is an acronym for Rocket-Digital Equalization System. It's designed to compensate for the construction, placement, or many other factors of a listener's room that may be severely contributing to detrimental subwoofer performance, and presentation.

    R-DES can also perform other benefits as well, such as a very high degree of subwoofer manipulation through parametric equalization, but the overall goal is a simple one: The listener's ROOM has an immense effect on a good (or bad) listening experience, especially in regards to lower frequencies.

    "The first version
    will be manually tuned by the listener using test-tone discs and an SPL meter. Upcoming versions will be self-tuning! Yep, I said it...
    self-tuning!"

    -- Mark L. Schifter

    We don't want to let our room detract from, or lessen our listening experience. We have to work with it, so we need something that can help tame it, and work synergistically with the whole system to provide as close to a perfect listening environment as possible. The integration of loudspeakers into any room has always been a problem, and again, especially with bass frequencies which are affected most by the room itself.

    This is something that we've lived with for a long time. It's something that I've thought long and hard about -- but how to do it in an effective and affordable way was the trick.

    With advances in DSP (Digital Signal Processing) technology, we have found a very cool, effective, and affordable way to correct those problems with a software/hardware solution. R-DES IS that solution. It will help greatly with not only the correct placement of a subwoofer or subwoofers within the room (which is extremely important in itself), but in addition, provide an incredibly effective tool for precise tuning of the subwoofer to the room. All of this is done utilizing the very user-friendly R-DES package consisting of an uncluttered, visually appealing, highly functional, software interface coupled with the R-DES hardware." MLS.

    This will allow you to store 4 curves/settings "in the box" and as many as you want on your computer which can be called up at will for a disc or even a particular song. A release date has not been announced yet but it should be relatively soon.

    Here's a link with some pics and discussion about R-DES:

    http://forum.av123.com/showthread.php?s=&threadid=4248
  • 08-12-2004, 05:54 AM
    Worf101
    Hey Tin.... good to see you gain my friend.
    Quote:

    Originally Posted by TinHere
    Here's a blurb from an e-mail about R-DES:

    "R-DES is an acronym for Rocket-Digital Equalization System. It's designed to compensate for the construction, placement, or many other factors of a listener's room that may be severely contributing to detrimental subwoofer performance, and presentation.

    R-DES can also perform other benefits as well, such as a very high degree of subwoofer manipulation through parametric equalization, but the overall goal is a simple one: The listener's ROOM has an immense effect on a good (or bad) listening experience, especially in regards to lower frequencies.

    "The first version
    will be manually tuned by the listener using test-tone discs and an SPL meter. Upcoming versions will be self-tuning! Yep, I said it...
    self-tuning!"

    -- Mark L. Schifter

    Very interesting post Tin. Thanks for the information and... good to see you again. Long time no see. I suppose you've been "hangin' out" at AV 123. How does it compare to here? Well good on ya mate and don't be a stranger...

    Da Worfster ;)
  • 08-12-2004, 08:37 AM
    TinHere
    Quote:

    Originally Posted by Worf101
    Very interesting post Tin. Thanks for the information and... good to see you again. Long time no see. I suppose you've been "hangin' out" at AV 123. How does it compare to here? Well good on ya mate and don't be a stranger...

    Da Worfster ;)

    Hey Worfster! Thanks for your reply. AV123 is a pleasant place to hang with folks who enjoy their products and appreciate the high level of customer service. As you might remember I was a supporter since my first interaction with them. It has been fun to watch the customer base grow and the product lines expand. Mark is an incredible individual and the people developing the products with him are cutting edge. Check it out. You don't have to own product to be welcome, but ya might get tempted to give them a shot after reading all the accolades. I know your aversion to buying new, but they do have great deals on b-stock. ;)

    Good seeing yer still at it. :)
  • 08-12-2004, 10:58 AM
    BillB
    I start off using my pre/pro's internal test tones to match the volume level of my sub with my main speakers using my Radio Shack analog sound level meter. I double check that setting with the "Subwoofer Blend" track on Delos' Surround Spectacular Test CD.

    I cross my speakers over to the sub at 60Hz in my pre/pro, bypassing the x-over in the sub. I start with a 1kHz tone at 80dB as a reference using Rives Audio's Test CD 2 which includes corrected 1/3 octave test tones for the errors of the RS meter. I note the dB level at the listening position for each frequency.

    My sub is adjustable from 0-180 degrees with 0=0, 180=8, eight "notches" or increments. I measure 20-100Hz at each "notch" until I get the flattest reading, that is where I set my phase. For me it ended up one notch below 90 degrees, resulting in a +4/-2dB range from 20-100Hz.

    Bill
  • 08-13-2004, 10:41 AM
    Richard Greene
    Scientific phase alignment based on bass frequency response measurements
    The best possible phase setting is the one that results in the smoothest measured bass
    frequency response at your listening seat.

    Measurements must be made using steady sine wave tones no more than 1/6 octave apart. Closer measurements would be better.

    The most common result with subwoofers located the same distance from your ears as the satellite speakers, will be the sub and satellites in phase.

    When listening to music the effects of a variable phase control are about the same as a
    simple two-way polarity switch. You're unlikely to hear a fine tuning effect with the variable phase control, but may hear a difference between in-phase versus 180 degrees out of phase, while listening to music that has content at or near the crossover frequency.
  • 08-13-2004, 11:48 AM
    topspeed
    Another long lost soul! Good to see you on the board, Rich. Your considerable knowledge and expertise has been sorely missed. Whatsa matta, Billy working you guys too hard ;)?

    Tinman, good to see you too! Don't be a stranger.